The invention relates to semiconductor devices for converting ionizing radiation into an electrical signal. The present ionizing radiation sensor has an n+-i-p+ structure, produced using the planar process. The sensor contains an i-region in the form of a high-resistivity substrate of high-purity float-zone silicon with p-type conductivity, having on its front face n+-regions (2, 3), an SiO2 layer (4), aluminium metallization (5), and a passivation layer. On the front face of the substrate (1) n-regions (2) are formed by ion implantation; a masking layer of SiO2 (layer 4) is grown; aluminium metallization (5) is deposited; and a passivation layer (6) is applied. At least one or more n+-regions (2) are situated in the central portion of the front face of the substrate and occupy most of the surface area, forming a sensitive zone of the sensor, and at least two n+-regions and two p+-regions are formed as annular elements (guard rings) (3), arranged concentrically in a non-sensitive zone along the periphery of the substrate (1), in order to reduce the amount of surface current and to provide for a smooth drop in potential from the sensitive region to the periphery of the device. The number of n+-regions (2) that form the matrix, i.e. the sensitive zone, of the sensor is equal to 2k, where k can be equal to 0—one region. Ports (9) for connecting leads are situated around the edges of the substrate in its non-sensitive region. The n+-regions (2) which form the sensitive zone of the sensor have profiled portions along the edges in the form of a series of recesses (12).